Experimental neuroprotection in ischemic stroke: a concise review

AMPA receptor modulation through sequential treatment with perampanel and aniracetam mitigates post-stroke damage in experimental model of ischemic stroke

The present study evaluates the effect of modulating α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor (AMPAR) by inhibiting them in the acute phase and activating them in the sub-acute phase on post-stroke recovery in middle cerebral artery occlusion (MCAo) model of stroke in rats. After 90 min of MCAo, perampanel (an AMPAR antagonist, 1.5 mg/kg i.p) and aniracetam (an AMPA agonist, 50 mg/kg i.p.) were administered for different durations after MCAo. Later, after obtaining the best time point for the antagonist and the agonist treatment protocols, sequential treatment with perampanel and aniracetam were given, and the effect on neurological damage and post stroke recovery were assessed. Perampanel and aniracetam significantly protected MCAo-induced neurological damage and diminished the infarct percentage. Furthermore, treatment with these study drugs improved the motor coordination and grip strength. Sequential treatment with perampanel and aniracetam reduced the infarct percentage as assessed by MRI. Moreover, these compounds diminished the inflammation via reducing the levels of pro-inflammatory cytokines (TNF-α, IL-1β) and increasing the levels of anti-inflammatory cytokine (IL-10) along with reductions in GFAP expression. Moreover, the neuroprotective markers (BDNF and TrkB) were found to be significantly increased. Levels of apoptotic markers (Bax, cleaved-caspase-3; Bcl2 and TUNEL positive cells) and neuronal damage (MAP-2) were normalized with the AMPA antagonist and agonist treatment. Expressions of GluR1 and GluR2 subunits of AMPAR were significantly enhanced with sequential treatment. The present study thus showed that modulation of AMPAR improves neurobehavioral deficits and reduces the infarct percentage through anti-inflammatory, neuroprotective and anti-apoptotic effects.

Neuroprotection for Nonarteritic Central Retinal Artery Occlusion: Lessons from Acute Ischemic Stroke

Nonarteritic central retinal artery occlusion (NA-CRAO) is a variant of acute ischemic stroke (AIS) and is a cause of sudden severe loss of vision. There are guidelines by the American Heart Association and the American Stroke Association for the care of CRAO patients. This review explores the basis of retinal neuroprotection for CRAO and its potential for improving the outcome of NA-CRAO. Recently, there have been significant advances in research into the use of neuroprotection to treat retinal diseases, including retinal detachment, age-related macular degeneration, and inherited retinal diseases. Also, neuroprotective research in AIS has been extensive, and newer drugs tested, including Uric acid, Nerinetide, and Otaplimastat, with promising results. Progress in cerebral neuroprotection after AIS offers hope for retinal neuroprotection after CRAO; and a possibility of extrapolating research findings from AIS into CRAO. Combining neuroprotection and thrombolysis can extend the therapeutic window for NA-CRAO treatment and potentially improve outcomes. Experimented neuroprotection for CRAO includes Angiopoietin (Comp Ang1), KUS 121, Gene therapy (XIAP), and hypothermia. Efforts in the field of neuroprotection for NA-CRAO should focus on better imaging to delineate the penumbra after an acute episode of NA-CRAO (using a combination of high-definition optical coherence angiography and electrophysiology). Also, research should explore details of pathophysiologic mechanisms involved in NA-CRAO, allowing for further neuroprotective intervention, and closing the gap between preclinical and clinical neuroprotection.

Pharmacological Strategies for Stroke Intervention: Assessment of Pathophysiological Relevance and Clinical Trials

OBJECTIVES

The present review describes stroke pathophysiology in brief and discusses the spectrum of available treatments with different promising interventions that are in clinical settings or are in clinical trials.

METHODS

Relevant articles were searched using Google Scholar, Cochrane Library, and PubMed. Keywords for the search included ischemic stroke, mechanisms, stroke interventions, clinical trials, and stem cell therapy.

RESULTS AND CONCLUSION

Stroke accounts to a high burden of mortality and morbidity around the globe. Time is an important factor in treating stroke. Treatment options are limited; however, agents with considerable efficacy and tolerability are being continuously explored. With the advances in stroke interventions, new therapies are being formulated with a hope that these may aid the ongoing protective and reparative processes. Such therapies may have an extended therapeutic time window in hours, days, weeks, or longer and may have the advantage to be accessible by a majority of the patients.

Synthesis and Pharmacological Evaluation of Novel Triazole-Pyrimidine Hybrids as Potential Neuroprotective and Anti-neuroinflammatory Agents

OBJECTIVE

Neuroprotection is a precise target for the treatment of neurodegenerative diseases, ischemic stroke, and traumatic brain injury. Pyrimidine and its derivatives have been proven to use antiviral, anticancer, antioxidant, and antimicrobial activity prompting us to study the neuroprotection and anti-inflammatory activity of the triazole-pyrimidine hybrid on human microglia and neuronal cell model.

METHODS

A series of novel triazole-pyrimidine-based compounds were designed, synthesized and characterized by mass spectra, 1HNMR, 13CNMR, and a single X-Ray diffraction analysis. Further, the neuroprotective, anti-neuroinflammatory activity was evaluated by cell viability assay (MTT), Elisa, qRT-PCR, western blotting, and molecular docking.

RESULTS

The molecular results revealed that triazole-pyrimidine hybrid compounds have promising neuroprotective and anti-inflammatory properties. Among the 14 synthesized compounds, ZA3-ZA5, ZB2-ZB6, and intermediate S5 showed significant anti-neuroinflammatory properties through inhibition of nitric oxide (NO) and tumor necrosis factor-α (TNF-α) production in LPS-stimulated human microglia cells. From 14 compounds, six (ZA2 to ZA6 and intermediate S5) exhibited promising neuroprotective activity by reduced expression of the endoplasmic reticulum (ER) chaperone, BIP, and apoptosis marker cleaved caspase-3 in human neuronal cells. Also, a molecular docking study showed that lead compounds have favorable interaction with active residues of ATF4 and NF-kB proteins.

CONCLUSION

The possible mechanism of action was observed through the inhibition of ER stress, apoptosis, and the NF-kB inflammatory pathway. Thus, our study strongly indicates that the novel scaffolds of triazole-pyrimidine-based compounds can potentially be developed as neuroprotective and anti-neuroinflammatory agents.

Lithium Biological Action Mechanisms after Ischemic Stroke

Lithium is a source of great scientific interest because although it has such a simple structure, relatively easy-to-analyze chemistry, and well-established physical properties, the plethora of effects on biological systems—which influence numerous cellular and molecular processes through not entirely explained mechanisms of action—generate a mystery that modern science is still trying to decipher. Lithium has multiple effects on neurotransmitter-mediated receptor signaling, ion transport, signaling cascades, hormonal regulation, circadian rhythm, and gene expression. The biochemical mechanisms of lithium action appear to be multifactorial and interrelated with the functioning of several enzymes, hormones, vitamins, and growth and transformation factors. The widespread and chaotic marketing of lithium salts in potions and mineral waters, always at inadequate concentrations for various diseases, has contributed to the general disillusionment with empirical medical hypotheses about the therapeutic role of lithium. Lithium salts were first used therapeutically in 1850 to relieve the symptoms of gout, rheumatism, and kidney stones. In 1949, Cade was credited with discovering the sedative effect of lithium salts in the state of manic agitation, but frequent cases of intoxication accompanied the therapy. In the 1960s, lithium was shown to prevent manic and also depressive recurrences. This prophylactic effect was first demonstrated in an open-label study using the “mirror” method and was later (after 1970) confirmed by several placebo-controlled double-blind studies. Lithium prophylaxis was similarly effective in bipolar and also unipolar patients. In 1967, the therapeutic value of lithemia was determined, included in the range of 0.5–1.5 mEq/L. Recently, new therapeutic perspectives on lithium are connected with improved neurological outcomes after ischemic stroke. The effects of lithium on the development and maintenance of neuroprotection can be divided into two categories: short-term effects and long-term effects. Unfortunately, the existing studies do not fully explain the lithium biological action mechanisms after ischemic stroke.

Targeting upregulated RNA binding protein RCAN1.1: a promising strategy for neuroprotection in acute ischemic stroke

Aims

To explore the expression changes and roles of the RNA‐binding protein RCAN1.1 in acute ischemic stroke (AIS), and to preliminarily confirm the medicinal value of the RNA aptamer R1SR13 in AIS by targeting RCAN1.1.

Methods

Two mouse AIS models of middle cerebral artery occlusion (MCAO) and right common carotid artery ligation (R‐CCAL) and oxygen glucose deprivation (OGD) model of AIS in primary neurons and SH‐SY5Y were performed. The expression pattern of RCAN1.1 was assessed using real‐time quantitative PCR (RT‐qPCR) and western blotting (WB) in vivo and in vitro. The underlying mechanism for the elevation of RCAN1.1 in the upstream was investigated. Lentiviruses were administrated and the effect of RCAN1.1 in AIS was assessed by ATP level, caspase 3/7 assay, TUNEL and WB. The protective function of R1SR13 in AIS was evaluated both in vivo and in vitro.

Results

In two mouse models of AIS, RCAN1.1 mRNA and RCAN1.1 L protein were significantly upregulated in the ischemic brain tissue. The same results were detected in the OGD model of primary neurons and SH‐SY5Y. The mechanistic analysis proved that hypoxia‐inducible factor‐1α (HIF1α) could specifically activate the RCAN1.1 gene promoter through combining with the functional hypoxia‐responsive element (HRE) site (−325 to −322 bp). The increased expression of RCAN1.1 L markedly depleted ATP production and aggravated neuronal apoptosis under OGD condition. R1SR13, an antagonizing RNA aptamer of RCAN1.1, was demonstrated to reduce neuronal apoptosis caused by the elevated RCAN1.1 L in the cellular and animal models of AIS.

Conclusion

RCAN1.1 is a novel target gene of HIF1α and the functional HRE in the RCAN1.1 promoter region is −325 to −322 bp. The marked upregulation of RCAN1.1 in AIS promoted neuronal apoptosis, an effect that could be reversed by its RNA aptamer R1SR13 in vivo and in vitro. Thus, R1SR13 represents a promising strategy for neuroprotection in AIS and our study lays a theoretical foundation for it to become a clinically targeted drug.

Chlorpromazine and Promethazine (C+P) Reduce Brain Injury after Ischemic Stroke through the PKC-δ/NOX/MnSOD Pathway

Cerebral ischemia-reperfusion (I/R) incites neurologic damage through a myriad of complex pathophysiological mechanisms, most notably, inflammation and oxidative stress. In I/R injury, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) produces reactive oxygen species (ROS), which promote inflammatory and apoptotic pathways, augmenting ROS production and promoting cell death. Inhibiting ischemia-induced oxidative stress would be beneficial for reducing neuroinflammation and promoting neuronal cell survival. Studies have demonstrated that chlorpromazine and promethazine (C+P) induce neuroprotection. This study investigated how C+P minimizes oxidative stress triggered by ischemic injury. Adult male Sprague-Dawley rats were subject to middle cerebral artery occlusion (MCAO) and subsequent reperfusion. 8 mg/kg of C+P was injected into the rats when reperfusion was initiated. Neurologic damage was evaluated using infarct volumes, neurological deficit scoring, and TUNEL assays. NOX enzymatic activity, ROS production, protein expression of NOX subunits, manganese superoxide dismutase (MnSOD), and phosphorylation of PKC-δ were assessed. Neural SHSY5Y cells underwent oxygen-glucose deprivation (OGD) and subsequent reoxygenation and C+P treatment. We also evaluated ROS levels and NOX protein subunit expression, MnSOD, and p-PKC-δ/PKC-δ. Additionally, we measured PKC-δ membrane translocation and the level of interaction between NOX subunit (p47^phox) and PKC-δ via coimmunoprecipitation. As hypothesized, treatment with C+P therapy decreased levels of neurologic damage. ROS production, NOX subunit expression, NOX activity, and p-PKC-δ/PKC-δ were all significantly decreased in subjects treated with C+P. C+P decreased membrane translocation of PKC-δ and lowered the level of interaction between p47^phox and PKC-δ. This study suggests that C+P induces neuroprotective effects in ischemic stroke through inhibiting oxidative stress. Our findings also indicate that PKC-δ, NOX, and MnSOD are vital regulators of oxidative processes, suggesting that C+P may serve as an antioxidant.

Neuroprotective effects of a 40% ethanol extract of the black walnut bark (Juglans nigra L.)

Introduction: Neuroprotection is a promising area of adjuvant therapy of ischemic brain lesions. At the same time, among potentially effective neuroprotectors, herbal remedies are distinguished due to their high efficiency and safety of use. In this work, some aspects of the neuroprotective effect of 40% ethanol extract of black walnut bark were investigated in comparison with its major component juglone.

Materials and methods: The work was performed on male Wistar rats, which were simulated with cerebral ischemia by irreversible occlusion of the middle cerebral artery. The acute toxicity of the extract was preliminarily evaluated. During the work, the following parameters were determined: changes in the behavior of animals in the Morris water maze, cerebral blood flow, brain necrosis zone area, the activity of mitochondrial complexes, citrate synthase activity, lactic, pyruvic, and ATP concentrations. The activity of the studied extract was compared with juglone in a concentration of 1 mg/kg (per os).

Discussion: The study showed that the use of black walnut bark extract in conditions of cerebral ischemia contributed to an increase in the activity of mitochondrial complexes I-V, citrate synthase, which in turn led to the normalization of aerobic-anaerobic metabolism reactions. The increase in the activity of respiratory complexes is probably mediated by the antioxidant properties of juglone, which is a major component of the test extract of black walnut bark.

Conclusion: Thus, the test extract can be a potentially effective neuroprotective agent and requires further study.

Histone Methyltransferases SUV39H1 and G9a and DNA Methyltransferase DNMT1 in Penumbra Neurons and Astrocytes after Photothrombotic Stroke

Background: Cerebral ischemia, a common cerebrovascular disease, is one of the great threats to human health and new targets for stroke therapy are needed. The transcriptional activity in the cell is regulated by epigenetic processes such as DNA methylation/demethylation, acetylation/deacetylation, histone methylation, etc. Changes in DNA methylation after ischemia can have both neuroprotective and neurotoxic effects depending on the degree of ischemia damage, the time elapsed after injury, and the site of methylation. Methods: In this study, we investigated the changes in the expression and intracellular localization of DNA methyltransferase DNMT1, histone methyltransferases SUV39H1, and G9a in penumbra neurons and astrocytes at 4 and 24 h after stroke in the rat cerebral cortex using photothrombotic stroke (PTS) model. Methods of immunofluorescence microscopy analysis, apoptosis analysis, and immunoblotting were used. Additionally, we have studied the effect of DNMT1 and G9a inhibitors on the volume of PTS-induced infarction and apoptosis of penumbra cells in the cortex of mice after PTS. Results: This study has shown that the level of DNMT1 increased in the nuclear and cytoplasmic fractions of the penumbra tissue at 24 h after PTS. Inhibition of DNMT1 by 5-aza-2′-deoxycytidine protected cells of PTS-induced penumbra from apoptosis. An increase in the level of SUV39H1 in the penumbra was found at 24 h after PTS and G9a was overexpressed at 4 and 24 h after PTS. G9a inhibitors A-366 and BIX01294 protected penumbra cells from apoptosis and reduced the volume of PTS-induced cerebral infarction. Conclusion: Thus, the data obtained show that DNA methyltransferase DNMT1 and histone methyltransferase G9a can be potential protein targets in ischemic penumbra cells, and their inhibitors are potential neuroprotective agents capable of protecting penumbra cells from postischemic damage to the cerebral cortex.

Effects of Alpha-2 Adrenergic Agonist Mafedine on Brain Electrical Activity in Rats after Traumatic Brain Injury

The search for and development of new neuroprotective (or cerebroprotective) drugs, as well as suitable methods for their preclinical efficacy evaluation, are priorities for current biomedical research. Alpha-2 adrenergic agonists, such as mafedine and dexmedetomidine, are a highly appealing group of drugs capable of reducing neurological deficits which result from brain trauma and vascular events in both experimental animals and human patients. Thus, our aim was to assess the effects of mafedine and dexmedetomidine on the brain’s electrical activity in a controlled cortical-impact model of traumatic brain injury (TBI) in rats. The functional status of the animals was assessed by electrocorticography (ECoG), using ECoG electrodes which were chronically implanted in different cortical regions. The administration of intraperitoneal mafedine sodium at 2.5 mg∙kg⁻¹ at 1 h after TBI induction, and daily for the following 6 days, restored interhemispheric connectivity in remote brain regions and intrahemispheric connections within the unaffected hemisphere at post-TBI day 7. Animals that had received mafedine sodium also demonstrated an improvement in cortical responses to photic and somatosensory stimulation. Dexmedetomidine at 25 μg∙kg⁻¹ did not affect the brain’s electrical activity in brain-injured rats. Our results confirm the previously described neuroprotective effects of mafedine sodium and suggest that ECoG registration and analysis are a viable method evaluating drug efficacy in experimental animal models of TBI.

The metabolic representation of ischemia in rat brain slices: A hyperpolarized 13 C magnetic resonance study

The ischemic penumbra in stroke is not clearly defined by today's available imaging tools. This study aimed to develop a model system and noninvasive biomarkers of ischemic brain tissue for an examination that might potentially be performed in humans, very quickly, in the course of stroke triage. Perfused rat brain slices were used as a model system and 31 P spectroscopy verified that the slices were able to recover from an ischemic insult of about 3.5 min of perfusion arrest. This was indicated as a return to physiological pH and adenosine triphosphate levels. Instantaneous changes in lactate dehydrogenase (LDH) and pyruvate dehydrogenase (PDH) activities were monitored and quantified by the metabolic conversions of hyperpolarized [1-13 C]pyruvate to [1-13 C]lactate and [13 C]bicarbonate, respectively, using 13 C spectroscopy. In a control group (n = 8), hyperpolarized [1-13 C]pyruvate was administered during continuous perfusion of the slices. In the ischemia group (n = 5), the perfusion was arrested 30 s prior to administration of hyperpolarized [1-13 C]pyruvate and perfusion was not resumed throughout the measurement time (approximately 3.5 min). Following about 110 s of the ischemic insult, LDH activity increased by 80.4 ± 13.5% and PDH activity decreased by 47.8 ± 25.3%. In the control group, the mean LDH/PDH ratio was 16.6 ± 3.3, and in the ischemia group, the LDH/PDH ratio reached an average value of 38.7 ± 16.9. The results suggest that monitoring the activity of LDH and PDH, and their relative activities, using hyperpolarized [1-13 C]pyruvate, could serve as an imaging biomarker to characterize the changes in the ischemic penumbra.

Tyrosol as a Neuroprotector: Strong Effects of a "Weak" Antioxidant

The use of neuroprotective agents for stroke is pathogenetically justified, but the translation of the results of preclinical studies of neuroprotectors into clinical practice has been a noticeable failure. One of the leading reasons for these failures is the one-target mechanism of their activity. p-Tyrosol (Tyr), a biophenol, is present in a variety of natural sources, mainly in foods, such as olive oil and wine. Tyr has a wide spectrum of biological activity: antioxidant, stress-protective, anti-inflammatory, anticancer, cardioprotective, neuroprotective and many others. This review analyzes data on the neuroprotective, antioxidant, anti-inflammatory, anti-apoptotic and other kinds of Tyr activity as well as data on the pharmacokinetics of the substance. The data presented in the review substantiate the acceptability of tyr as the basis for the development of a new neuroprotective drug with multitarget activity for the treatment of ischemic stroke. Tyr is a promising molecule for the development of an effective neuroprotective agent for use in ischemic stroke.

Dietary Nutrients and Prevention of Alzheimer's disease

Alzheimer's disease is an irrevocable, progressive brain disorder that gradually destroys memory and cognitive skills. One of the extensively studied method of preventing Alzheimer's disease (AD) disease progression is by providing nutritional diet. Several reports have shown that intake of nutritional elements as huperzine A, ursolic acid, vitamins etc. can directly influence pathogenesis of AD. Surprisingly, occurrence of metabolic disorders due to unhealthy diet has been known to be a major environmental causes for AD. It has been noted that AD disease severity can be controlled by supplementing dietary supplements containing huge amounts of health-promoting ingredients. These elements promote cell health, regeneration, and the anti-aging process that specifically interrupt the pathogenic pathways in AD development. Fortunately, incorporating changes in the nutritional content is inexpensive, easy, acceptable, safe, effective, and in most cases free from major adverse events. Many nutritional phytoconstituents such as flavonoids, alkaloids, and terpenoids are still being evaluated in the hope of identifying a successful therapy for AD. This review discusses the therapeutical potential of several key nutrients that have been researched for treating AD treatment and the method of their neuroprotective intervention.

Adjuvant High-Flow Normobaric Oxygen After Mechanical Thrombectomy for Anterior Circulation Stroke: a Randomized Clinical Trial

Adjuvant neuroprotective therapies for acute ischemic stroke (AIS) have demonstrated benefit in animal studies, albeit without human translation. We investigated the safety and efficacy of high-flow normobaric oxygen (NBO) after endovascular recanalization in anterior circulation stroke. This is a prospective randomized controlled study. Eligible patients were randomized to receive high-flow NBO by a Venturi mask (FiO2 50%, flow 15 L/min) or routine low-flow oxygen supplementation by nasal cannula (flow 3 L/min) after vessel recanalization for 6 h. Patient demographics, procedural metrics, complications, functional outcomes, symptomatic intracranial hemorrhage (sICH), and infarct volume were assessed. A total of 91 patients were treated with high-flow NBO. NBO treatment revealed a common odds ratio of 2.2 (95% CI, 1.26 to 3.87) favoring the distribution of global disability scores on the mRS at 90 days. The mortality at 90 days was significantly lower in the NBO group than in the control group, with an absolute difference of 13.86% (rate ratio, 0.35; 95% CI, 0.13-0.93). A significant reduction of infarct volume as determined by MRI was noted in the NBO group. The median infarct volume was 9.4 ml versus 20.5 ml in the control group (beta coefficient, - 20.24; 95% CI, - 35.93 to - 4.55). No significant differences were seen in the rate of sICH, pneumonia, urinary infection, and seizures between the 2 groups. This study suggests that high-flow NBO therapy after endovascular recanalization is safe and effective in improving functional outcomes, decreasing mortality, and reducing infarct volumes in anterior circulation stroke patients within 6 h from stroke onset.

LIM kinase inhibitor T56-LIMKi protects mouse brain from photothrombotic stroke

Primary Objective: In an ischemic stroke, the damage spreads from the infarction core to surrounding tissues. The present work was aimed at the search of effective neuroprotectors that restrict injury propagation. Research Design: We studied possible protective effects of inhibitors of protein kinases LIMK2 (T56-LIMKi), DYRK1A (harmine), and tryptophan hydroxylase (4-chlorophenylalanine) on infarction size and morphology of peri-infarct area after photothrombotic stroke (a model of ischemic stroke) in mouse brain. Methods and Procedures: Photothrombotic stroke was induced by laser irradiation of mouse cortex after administration of photosensitizer Bengal Rose, which does not penetrate cells and remains in blood vessels. Under light exposure, it induces vessel occlusion. Infarct volume and histological changes in the cerebral cortex were evaluated 3, 7 and 14 days after photothrombotic impact. Main Outcomes and Results: Harmine and 4-chlorophenylalanine did not influence infarct volume and morphology of peri-infarct area in the mouse brain cortex after photothrombotic stroke. However, LIMK2 inhibitor T56-LIMKi significantly reduced infarct volume 7 and 14 days after photothrombotic stroke. It also increased the percent of normochromic neurons and decreased the fraction of altered cortical cells (hypochromic, hyperchromic and pyknotic neurons). Conclusions: T56-LIMK2i may be considered as a promising anti-stroke agent.

A Systematic Review and Meta-Analysis of Animal Studies Testing Intra-Arterial Chilled Infusates After Ischemic Stroke

Background: As not all ischemic stroke patients benefit from currently available treatments, there is considerable need for neuroprotective co-therapies. Therapeutic hypothermia is one such co-therapy, but numerous issues have hampered its clinical use (e.g., pneumonia risk with whole-body cooling). Some problems may be avoided with brain-specific methods, such as intra-arterial selective cooling infusion (IA-SCI) into the arteries supplying the ischemic tissue. Objective: Our research question was about the efficacy of IA-SCI in animal middle cerebral artery occlusion models. We hypothesized that IA-SCI would be beneficial, but translationally-relevant study elements may be missing (e.g., aged animals). Methods: We completed a systematic review of the PubMed database following the PRISMA guidelines on May 21, 2020 for animal studies that administered IA-SCI in the peri-reperfusion period and assessed infarct volume, behavior (primary meta-analytic endpoints), edema, or blood-brain barrier injury (secondary endpoints). Our search terms included: "focal ischemia" and related terms, "IA-SCI" and related terms, and "animal" and related terms. Nineteen studies met inclusion criteria. We adapted a methodological quality scale from 0 to 12 for experimental design assessment (e.g., use of blinding/randomization, a priori sample size calculations). Results: Studies were relatively homogenous (e.g., all studies used young, healthy animals). Some experimental design elements, such as blinding, were common whereas others, such as sample size calculations, were infrequent (median methodological quality score: 5; range: 2-7). Our analyses revealed that IA-SCI provides benefit on all endpoints (mean normalized infarct volume reduction = 23.67%; 95% CI: 19.21-28.12; mean normalized behavioral improvement = 35.56%; 95% CI: 25.91-45.20; mean standardized edema reduction = 0.95; 95% CI: 0.56-1.34). Unfortunately, blood-brain barrier assessments were uncommon and could not be analyzed. However, there was substantial statistical heterogeneity and relatively few studies. Therefore, exploration of heterogeneity via meta-regression using saline infusion parameters, study quality, and ischemic duration was inconclusive. Conclusion: Despite convincing evidence of benefit in ischemic stroke models, additional studies are required to determine the scope of benefit, especially when considering additional elements (e.g., dosing characteristics). As there is interest in using this treatment alongside current ischemic stroke therapies, more relevant animal studies will be critical to inform patient studies.

Exogenous recombinant Hsp70 mediates neuroprotection after photothrombotic stroke

Ischaemic stroke is an acute interruption of the blood supply to the brain, which leads to rapid irreversible damage to nerve tissue. Ischaemic stroke is accompanied by the development of neuroinflammation and neurodegeneration observed around the affected brain area. Heat shock protein 70 (Hsp70) facilitates cell survival under a variety of different stress conditions. Hsp70 may be secreted from cells and exhibits cytoprotective activity. This activity most likely occurs by decreasing the levels of several proinflammatory cytokines through interaction with a few receptors specific to the innate immune system. Herein, we demonstrated that intranasal administration of recombinant human Hsp70 shows a significant twofold decrease in the volume of local ischaemia induced by photothrombosis in the mouse prefrontal brain cortex. Our results revealed that intranasal injections of recombinant Hsp70 decreased the apoptosis level in the ischaemic penumbra, stimulated axonogenesis and increased the number of neurons producing synaptophysin. Similarly, in the isolated crayfish stretch receptor, consisting of a single sensory neuron surrounded by the glial envelope, exogenous Hsp70 significantly decreased photoinduced apoptosis and necrosis of glial cells. The obtained data enable one to consider human recombinant Hsp70 as a promising compound that could be translated from the bench into clinical therapies.

Impact of aging and comorbidities on ischemic stroke outcomes in preclinical animal models: A translational perspective

Ischemic stroke is a highly complex and devastating neurological disease. The sudden loss of blood flow to a brain region due to an ischemic insult leads to severe damage to that area resulting in the formation of an infarcted tissue, also known as the ischemic core. This is surrounded by the peri-infarct region or penumbra that denotes the functionally impaired but potentially salvageable tissue. Thus, the penumbral tissue is the main target for the development of neuroprotective strategies to minimize the extent of ischemic brain damage by timely therapeutic intervention. Given the limitations of reperfusion therapies with recombinant tissue plasminogen activator or mechanical thrombectomy, there is high enthusiasm to combine reperfusion therapy with neuroprotective strategies to further reduce the progression of ischemic brain injury. Till date, a large number of candidate neuroprotective drugs have been identified as potential therapies based on highly promising results from studies in rodent ischemic stroke models. However, none of these interventions have shown therapeutic benefits in stroke patients in clinical trials. In this review article, we discussed the urgent need to utilize preclinical models of ischemic stroke that more accurately mimic the clinical conditions in stroke patients by incorporating aged animals and animal stroke models with comorbidities. We also outlined the recent findings that highlight the significant differences in stroke outcome between young and aged animals, and how major comorbid conditions such as hypertension, diabetes, obesity and hyperlipidemia dramatically increase the vulnerability of the brain to ischemic damage that eventually results in worse functional outcomes. It is evident from these earlier studies that including animal models of aging and comorbidities during the early stages of drug development could facilitate the identification of neuroprotective strategies with high likelihood of success in stroke clinical trials.

Citicoline for treating people with acute ischemic stroke

BACKGROUND

Stroke is one of the leading causes of long-lasting disability and mortality and its global burden has increased in the past two decades. Several therapies have been proposed for the recovery from, and treatment of, ischemic stroke. One of them is citicoline. This review assessed the benefits and harms of citicoline for treating patients with acute ischemic stroke.

OBJECTIVES

To assess the clinical benefits and harms of citicoline compared with placebo or any other control for treating people with acute ischemic stroke.

SEARCH METHODS

We searched in the Cochrane Stroke Group Trials Register, CENTRAL, MEDLINE Ovid, Embase Ovid, LILACS until 29 January 2020. We searched the World Health Organization Clinical Trials Search Portal and ClinicalTrials.gov. Additionally, we also reviewed reference lists of the retrieved publications and review articles, and searched the websites of the US Food and Drug Administration (FDA) and European Medicines Agency (EMA).

SELECTION CRITERIA

We included randomized controlled trials (RCTs) in any setting including participants with acute ischemic stroke. Trials were eligible for inclusion if they compared citicoline versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

We selected RCTs, assessed the risk of bias in seven domains, and extracted data by duplicate. Our primary outcomes of interest were all-cause mortality and the degree of disability or dependence in daily activities at 90 days. We estimated risk ratios (RRs) for dichotomous outcomes. We measured statistical heterogeneity using the I² statistic. We conducted our analyses using the fixed-effect and random-effects model meta-analyses. We assessed the overall quality of evidence for six pre-specified outcomes using the GRADE approach.

MAIN RESULTS

We identified 10 RCTs including 4281 participants. In all these trials, citicoline was given either orally, intravenously, or a combination of both compared with placebo or standard care therapy. Citicoline doses ranged between 500 mg and 2000 mg per day. We assessed all the included trials as having high risk of bias. Drug companies sponsored six trials. A pooled analysis of eight trials indicates there may be little or no difference in all-cause mortality comparing citicoline with placebo (17.3% versus 18.5%; RR 0.94, 95% CI 0.83 to 1.07; I² = 0%; low-quality evidence due to risk of bias). Four trials found no difference in the proportion of patients with disability or dependence in daily activities according to the Rankin scale comparing citicoline with placebo (21.72% versus 19.23%; RR 1.11, 95% CI 0.97 to 1.26; I² = 1%; low-quality evidence due to risk of bias). Meta-analysis of three trials indicates there may be little or no difference in serious cardiovascular adverse events comparing citicoline with placebo (8.83% versus 7.77%; RR 1.04, 95% CI 0.84 to 1.29; I² = 0%; low-quality evidence due to risk of bias). Overall, either serious or non-serious adverse events - central nervous system, gastrointestinal, musculoskeletal, etc. - were poorly reported and harms may have been underestimated. Four trials assessing functional recovery with the Barthel Index at a cut-off point of 95 points or more did not find differences comparing citicoline with placebo (32.78% versus 30.70%; RR 1.03, 95% CI 0.94 to 1.13; I² = 24%; low-quality evidence due to risk of bias). There were no differences in neurological function (National Institutes of Health Stroke Scale at a cut-off point of ≤ 1 points) comparing citicoline with placebo according to five trials (24.31% versus 22.44%; RR 1.08, 95% CI 0.96 to 1.21; I² = 27%, low-quality evidence due to risk of bias). A pre-planned Trial Sequential Analysis suggested that no more trials may be needed for the primary outcomes but no trial provided information on quality of life.

AUTHORS' CONCLUSIONS

This review assessed the clinical benefits and harms of citicoline compared with placebo or any other standard treatment for people with acute ischemic stroke. The findings of the review suggest there may be little to no difference between citicoline and its controls regarding all-cause mortality, disability or dependence in daily activities, severe adverse events, functional recovery and the assessment of the neurological function, based on low-certainty evidence. None of the included trials assessed quality of life and the safety profile of citicoline remains unknown. The available evidence is of low quality due to either limitations in the design or execution of the trials.

Apoptosis regulation in the penumbra after ischemic stroke: expression of pro- and antiapoptotic proteins

Ischemic stroke is the leading cause of human disability and mortality in the world. The main problem in stroke therapy is the search of efficient neuroprotector capable to rescue neurons in the potentially salvageable transition zone (penumbra), which is expanding after brain damage. The data on molecular mechanisms of penumbra formation and expression of diverse signaling proteins in the penumbra during first 24 h after ischemic stroke are discussed. Two basic features of cell death regulation in the ischemic penumbra were observed: (1) both apoptotic and anti-apoptotic proteins are simultaneously over-expressed in the penumbra, so that the fate of individual cells is determined by the balance between these opposite tendencies. (2) Similtaneous and concerted up-regulation in the ischemic penumbra of proteins that execute apoptosis (caspases 3, 6, 7; Bcl-10, SMAC/DIABLO, AIF, PSR), signaling proteins that regulate different apoptosis pathways (p38, JNK, DYRK1A, neurotrophin receptor p75); transcription factors that control expression of various apoptosis regulation proteins (E2F1, p53, c-Myc, GADD153); and proteins, which are normally involved in diverse cellular functions, but stimulate apoptosis in specific situations (NMDAR2a, Par4, GAD65/67, caspase 11). Hence, diverse apoptosis initiation and regulation pathways are induced simultaneously in penumbra from very different initial positions. Similarly, various anti-apoptotic proteins (Bcl-x, p21/WAF-1, MDM2, p63, PKBα, ERK1, RAF1, ERK5, MAKAPK2, protein phosphatases 1α and MKP-1, estrogen and EGF receptors, calmodulin, CaMKII, CaMKIV) are upregulated. These data provide an integral view of neurodegeneration and neuroprotection in penumbra. Some discussed proteins may serve as potential targets for anti-stroke therapy.

Overexpression of HDAC6, but not HDAC3 and HDAC4 in the penumbra after photothrombotic stroke in the rat cerebral cortex and the neuroprotective effects of α-phenyl tropolone, HPOB, and sodium valproate

Epigenetic processes play important roles in brain responses to ischemic injury. We studied effects of photothrombotic stroke (PTS, a model of ischemic stroke) on the intracellular level and cellular localization of histone deacetylases HDAC3, HDAC4 and HDAC6 in the rat brain cortex, and tested the potential neuroprotector ability of their inhibitors. The background level of HDAC3, HDAC4 and HDAC6 in the rat cerebral cortex was relatively low. HDAC3 localized in the nuclei of some neurons and few astrocytes. HDAC4 was found in the neuronal cytoplasm. After PTS, their levels in penumbra did not change, but HDAC4 appeared in the nuclei of some cells. Its level in the cytoplasmic, but not nuclear fraction of penumbra decreased at 24, but not 4 h after PTS. HDAC6 was upregulated in neurons and astrocytes in the PTS-induced penumbra, especially in the nuclear fraction. Unlike HDAC3 and HDAC4, HDAC6 co-localized with TUNEL-positive apoptotic cells. Inhibitory analysis confirmed the involvement of HDAC6, but not HDAC3 and HDAC4 in neurodegeneration. HDAC6 inhibitor HPOB, HDAC2/8 inhibitor α-phenyl tropolone, and non-specific histone deacetylase inhibitor sodium valproate, but not HDAC3 inhibitor BRD3308, or HDAC4 inhibitor LMK235, decreased PTS-induced infarction volume in the mouse brain, reduced apoptosis, and recovered the motor behavior. HPOB also restored PTS-impaired acetylation of α-tubulin. α-phenyl tropolone restored acetylation of histone H4 in penumbra cells. These results suggest that histone deacetylases HDAC6 and HDAC2 are the possible molecular targets for anti-ischemic therapy, and their inhibitors α-phenyl tropolone, HBOP and sodium valproate can be considered as promising neuroprotectors.

Materials to Promote Recovery After Stroke

Stroke is the leading cause of long-term disability with no current treatment addressing post-stroke disability. The complex pathophysiology of stroke and the brain's limited potential for regeneration prevents sufficient endogenous repair for complete recovery. While engineered materials provide an exciting opportunity to augment endogenous repair in conjunction with other therapies that address post-stroke disability, much of the preclinical work in this arena is still in its infancy. Biomaterials can be used to enhance drug- or stem cell-sustained and targeted delivery. Moreover, materials can act as extracellular matrix-mimics and augment a pro-repair environment by addressing astrogliosis, inflammation, neurogenesis, axonal sprouting, and angiogenesis. Lastly, there is a growing need to elucidate stroke repair mechanisms to identify novel targets to inform material design for brain repair after stroke.

Neuroinflammation: friend and foe for ischemic stroke

Stroke, the third leading cause of death and disability worldwide, is undergoing a change in perspective with the emergence of new ideas on neurodegeneration. The concept that stroke is a disorder solely of blood vessels has been expanded to include the effects of a detrimental interaction between glia, neurons, vascular cells, and matrix components, which is collectively referred to as the neurovascular unit. Following the acute stroke, the majority of which are ischemic, there is secondary neuroinflammation that both promotes further injury, resulting in cell death, but conversely plays a beneficial role, by promoting recovery. The proinflammatory signals from immune mediators rapidly activate resident cells and influence infiltration of a wide range of inflammatory cells (neutrophils, monocytes/macrophages, different subtypes of T cells, and other inflammatory cells) into the ischemic region exacerbating brain damage. In this review, we discuss how neuroinflammation has both beneficial as well as detrimental roles and recent therapeutic strategies to combat pathological responses. Here, we also focus on time-dependent entry of immune cells to the ischemic area and the impact of other pathological mediators, including oxidative stress, excitotoxicity, matrix metalloproteinases (MMPs), high-mobility group box 1 (HMGB1), arachidonic acid metabolites, mitogen-activated protein kinase (MAPK), and post-translational modifications that could potentially perpetuate ischemic brain damage after the acute injury. Understanding the time-dependent role of inflammatory factors could help in developing new diagnostic, prognostic, and therapeutic neuroprotective strategies for post-stroke inflammation.

Characterization and Imaging of Lipid-Shelled Microbubbles for Ultrasound-Triggered Release of Xenon

Xenon (Xe) is a bioactive gas capable of reducing and stabilizing neurologic injury in stroke. The goal of this work was to develop lipid-shelled microbubbles for xenon loading and ultrasound-triggered release. Microbubbles loaded with either xenon (Xe-MB) or xenon and octafluoropropane (Xe-OFP-MB) (9:1 v/v) were synthesized by high-shear mixing. The size distribution and the frequency-dependent attenuation coefficient of Xe-MB and Xe-OFP-MB were measured using a Coulter counter and a broadband acoustic attenuation spectroscopy system, respectively. The Xe dose was evaluated using gas chromatography/mass spectrometry. The total Xe doses in Xe-MB and Xe-OFP-MB were 113.1 ± 13.5 and 145.6 ± 25.5 μl per mg of lipid, respectively. Co-encapsulation of OFP increased the total xenon dose, attenuation coefficient, microbubble stability (in an undersaturated solution), and shelf life of the agent. Triggered release of gas payload was demonstrated with 6-MHz duplex Doppler and 220-kHz pulsed ultrasound. These results constitute the first step toward the use of lipid-shelled microbubbles for applications such as neuroprotection in stroke.

Mild Acidosis Protects Neurons during Oxygen-Glucose Deprivation by Reducing Loss of Mitochondrial Respiration

Brain ischemia is often accompanied by brain acidosis and this acidosis can affect ischemic neuronal injury. Ischemic neuronal injury is initiated by a decrease in ATP production which mainly relies on mitochondrial oxidative phosphorylation. Ischemia often causes mitochondrial dysfunction, and acidosis has been found to affect mitochondrial function, suggesting that acidosis accompanying ischemia may influence neurons by targeting mitochondrial metabolism. However, the effects of acidosis on mitochondrial energy metabolism during ischemia lacks thorough investigation. Here, we found that mild acidosis significantly reduced neuronal death possibly by slowing the process of ATP deprivation during oxygen-glucose deprivation (OGD), an in vitro ischemic model. The maintaining of neuronal ATP depended on protecting mitochondrial ATP production. Further investigation of mitochondrial function revealed that mild acidosis alleviated OGD-induced collapse of mitochondrial membrane potentials as well as damage to respiratory function, at least in part by reducing impacts on complex I and II activities. Inhibition of complex I activity aggravated neuronal death, which suggests that the contribution of mild acidosis to maintaining complex I activity promoted neuronal survival during OGD. Our findings reveal maintaining mitochondrial respiration as a new possible protective mechanism of mild acidosis during ischemia, on neurons.

The endocannabinoid system and stroke: A focused review

Stroke is an important cause of morbidity and mortality worldwide. Development of novel neuroprotectants is of paramount importance. This review seeks to summarize the recent evidence for the role of the endocannabinoid signaling system in stroke pathophysiology, as well as the evidence from preclinical studies regarding the efficacy of cannabinoids as neuroprotective therapies in the treatment of stroke. Recent evidence from rodent models implicating cannabinoid 1 receptor (CB1R), cannabinoid 2 receptor (CB2R), and CB1R and CB2R co-antagonism as neuroprotective strategies in stroke are reviewed. Rodent evidence for the therapeutic role of the endocannabinoid system in treating poststroke depression is reviewed. Finally, evidence for the role of cannabidiol, a publicly available cannabinoid that does not bind directly to known endocannabinoid receptors, as a stroke neuroprotectant is also reviewed. The review closes with a consideration of the role of human cannabinoid abuse in stroke and considers future directions for research on endocannabinoid-based stroke therapeutics.

Delivery of xenon-containing echogenic liposomes inhibits early brain injury following subarachnoid hemorrhage

Xenon (Xe), a noble gas, has promising neuroprotective properties with no proven adverse side-effects. We evaluated neuroprotective effects of Xe delivered by Xe-containing echogenic liposomes (Xe-ELIP) via ultrasound-controlled cerebral drug release on early brain injury following subarachnoid hemorrhage (SAH). The Xe-ELIP structure was evaluated by ultrasound imaging, electron microscopy and gas chromatography-mass spectroscopy. Animals were randomly divided into five groups: Sham, SAH, SAH treated with Xe-ELIP, empty ELIP, or Xe-saturated saline. Treatments were administrated intravenously in combination with ultrasound application over the common carotid artery to trigger Xe release from circulating Xe-ELIP. Hematoma development was graded by SAH scaling and quantitated by a colorimetric method. Neurological evaluation and motor behavioral tests were conducted for three days following SAH injury. Ultrasound imaging and electron microscopy demonstrated that Xe-ELIP have a unique two-compartment structure, which allows a two-stage Xe release profile. Xe-ELIP treatment effectively reduced bleeding, improved general neurological function, and alleviated motor function damage in association with reduced apoptotic neuronal death and decreased mortality. Xe-ELIP alleviated early SAH brain injury by inhibiting neuronal death and bleeding. This novel approach provides a noninvasive strategy of therapeutic gas delivery for SAH treatment.

The cerebral circulation and cerebrovascular disease III: Stroke

In this paper, our review series on cerebrovascular disease anatomy, physiology, and pathology ends with a thorough discussion of the most significant cerebrovascular pathology: stroke. This discussion proceeds through two layers of organization. First, stroke is divided up into its main etiologic categories (ischemic stroke/transient ischemic attack, hemorrhagic stroke, and ischemic to hemorrhagic transformation). Then, the epidemiological, pathophysiological, clinical, and therapeutic (employed currently as well as emerging) aspects of each etiology are explored; emphasis is placed upon the therapeutic aspects. Finally, once we have covered all aspects of each etiologic category, we end our review with a defense of the thesis that there is much hope for the future of stroke treatment to be derived from familiarity with the literature on emerging therapies.